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Serviceability limit state of vibrations in under-deck cable-stayed bridges accounting for vehicle-structure interaction
Verification of the serviceability limit state of vibrations due to traffic live loads can be neglected in conventional types of concrete road bridges but becomes critical in the design of slender structures like under-deck cable-stayed bridges. The novelty of the work presented in this article is that an innovative vehicle-bridge interaction model is employed, in which realistic wheel dimensions of heavy trucks, road roughness profiles and the cross slope of the road are considered in nonlinear dynamic analyses of detailed three-dimensional finite element models. An extensive parametric study is conducted to explore the influence of the bridge parameters such as the longitudinal and transverse cable arrangement and the support conditions, in addition to the load modelling, road quality, the wheel size, the transverse road slope and the vehicle position and speed on the response of under-deck cable-stayed bridges. It has been observed that the vibrations perceived by pedestrians can be effectively reduced by concentrating the cable-system below the deck at the bridge centreline. The Fourier amplitude spectrum of the acceleration at critical positions along the deck proved that the response of under-deck cable-stayed bridges is not dominated only by contributions at the fundamental mode and, consequently, the conventional deflection-based methods are not valid to assess the users comfort. Instead, Vehicle-Bridge Interaction analyses are recommended for detailed design, considering the wheel dimensions if the pavement quality is bad and/or if the wheel radius is large. Finally, we verify through multiple approaches that the comfort of pedestrian users is more critical than that of vehicle users. However, the comfort of vehicle users is shown to be significantly affected when the road quality is poor
Performance genotípica de variedades de cana-de-açúcar inoculadas com bactérias diazotróficas endofíticas.
A fixação biológica do nitrogênio (FBN) pode substituir entre 10 a 30% do fertilizante nitrogenado aplicado na cultura da cana-de-açúcar, este valor pode ser aumentado se considerarmos a seleção de genótipos de cana-de-açúcar com maior potencial de fixação biológica de nitrogênio. Mas para que isso aconteça fazem-se necessárias estratégias que permitam maximizar a escolha desses materiais como a seleção de variedades responsivas à fixação biológica do nitrogênio. Assim, buscou-se no presente trabalho avaliar a resposta de variedades de cana-de-açúcar quanto à inoculação com bactérias diazotróficas endofíticas. Foi conduzido um ensaio fatorial (16x3) com 16 cultivares e três fatores de avaliação, sendo com inoculação, com adubação com 120 kg de n/ha, e sem adubação e sem inoculação. Houve diferenças significativas entre variedades e fatores de avaliação para os caracteres avaliados, com destaque para as variedades SP716949 e SP784764. As variedades apresentaram responsividade variada quanto ao uso de inoculante, evidenciando a necessidade de em plantios comerciais, identificar o melhor arranjo para a Fixação Biológica do Nitrogênio visando incremento na produtividade e redução de custos
Moduli stabilization and uplifting with dynamically generated F-terms
We use the F-term dynamical supersymmetry breaking models with metastable
vacua in order to uplift the vacuum energy in the KKLT moduli stabilization
scenario. The main advantage compared to earlier proposals is the manifest
supersymmetric treatment and the natural coexistence of a TeV gravitino mass
with a zero cosmological constant. We argue that it is generically difficult to
avoid anti de-Sitter supersymmetric minima, however the tunneling rate from the
metastable vacuum with zero vacuum energy towards them can be very suppressed.
We briefly comment on the properties of the induced soft terms in the
observable sector.Comment: 18 pages, no figures Comments and one reference adde
Role of quantum coherence in chromophoric energy transport
The role of quantum coherence and the environment in the dynamics of
excitation energy transfer is not fully understood. In this work, we introduce
the concept of dynamical contributions of various physical processes to the
energy transfer efficiency. We develop two complementary approaches, based on a
Green's function method and energy transfer susceptibilities, and quantify the
importance of the Hamiltonian evolution, phonon-induced decoherence, and
spatial relaxation pathways. We investigate the Fenna-Matthews-Olson protein
complex, where we find a contribution of coherent dynamics of about 10% and of
relaxation of 80%.Comment: 5 pages, 3 figures, included static disorder, correlated environmen
Stability of flux compactifications and the pattern of supersymmetry breaking
We extend the KKLT approach to moduli stabilization by including the dilaton
and the complex structure moduli into the effective supergravity theory.
Decoupling of the dilaton is neither always possible nor necessary for the
existence of stable minima with zero (or positive) cosmological constant. The
pattern of supersymmetry breaking can be much richer than in the decoupling
scenario of KKLT.Comment: References adde
Towards Minkowski Vacua in Type II String Compactifications
We study the vacuum structure of compactifications of type II string theories
on orientifolds with SU(3)xSU(3) structure. We argue that generalised geometry
enables us to treat these non-geometric compactifications using a supergravity
analysis in a way very similar to geometric compactifications. We find
supersymmetric Minkowski vacua with all the moduli stabilised at weak string
coupling and all the tadpole conditions satisfied. Generically the value of the
moduli fields in the vacuum is parametrically controlled and can be taken to
arbitrarily large values.Comment: 33 pages; v2 minor corrections, references added, version to appear
in JHE
A second look at N=1 supersymmetric AdS_4 vacua of type IIA supergravity
We show that a class of type IIA vacua recently found within the N=4
effective approach corresponds to compactification on Ads_4 \times S^3 \times
S^3/Z_2^3. The results obtained using the effective method completely match the
general ten-dimensional analysis for the existence of N=1 warped
compactifications on Ads_4 \times M_6. In particular, we verify that the
internal metric is nearly-Kahler and that for specific values of the parameters
the Bianchi identity of the RR 2-form is fulfilled without sources. For another
range of parameters, including the massless case, the Bianchi identity is
satisfied when D6-branes are introduced. Solving the tadpole cancellation
conditions in D=4 we are able to find examples of appropriate sets of branes.
In the second part of this paper we describe how an example with internal space
CP^3 but with non nearly-Kahler metric fits into the general analysis of flux
vacua.Comment: Latex file, 35 pages, no figures. Reference added, minor corrections
adde
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